Peter, would it be easier to fix it now, or later when it spins a rod bearing?
ARP bolts are marked on the heads, so there is no doubt (see photo above) The black color may or may not be indicative of heat treatment, or cheap black paint.
Everyone following this discussion should go to the ARP website and read the first 10 or 15 pages of their catalog. It’s a Readers Digest summary of a couple of semesters of engineering Material Science and Machine Design. A very worthwhile read. I would also recommend that anyone who owns a set of wrenches should also own a copy of Machinery’s Handbook.
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I love you Roger, but I laughed out loud when I read this! An oxymoron for the ages! 
Next up, the Y2k WiFi buggy whip!
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Roger,
I don’t understand your rationale…
Since Jaguar thought it was prudent to switch to a cotter less 12 point nut and new bolt in lieu of the castellated nut & bolt arrangement in use since 1949, wouldn’t it be advisable for the amateur enthusiast to do the same?
If the argument is that ARP doesn’t produce a specific replacement that doesn’t have to be tailored to suit, Jaguar still does offer new replacements which require no modification for the application.
Wouldn’t Jaguar supplied modern cotter less replacements be better than reusing old, possibly over stretched originals that will still require split pins?
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Now I’m sorry I ever mentioned it.
To use these ARP bolts, it looks to me like you will have to put a champfer or radius on the holes in the top side of the rods, and bore them out a little bit.
Any fastener nut system that doesn’t loosen up or break is a good system. Cotterless nuts replaced slotted nuts because they are faster to install, and on the production line time is money.
Replacing old bolts and nuts, if you don’t trust them for various reasons, with ultra high strength bolts, that you trust for various reasons, your extra money buys you peace of mind.
For my peace of mind, I trust Heynes, Bailey, and my own inspection, measurements and engineering calculations.
We’ve had this argument a few times before.
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There might be a Ph.D., in reactive/repetitive psychology, to be had here…
Doug,
No problems at all using genuine Jaguar replacement bolts and split-pin less 12 point nuts, given they are designed/manufactured specifically for an XK engine application.
But I do have a problem using any bolts/nuts made by other companies for other applications, being deemed suitable by a salesman as being OK to use in an XK engine, especially when people start getting out a file etc to make them fit.
But still easiest solution, is to reuse your original bolts and slotted nuts and new (imperial size) split-pins, if they all pass a physical inspection for damage/corrosion. My local Jaguar Dealership, does not sell any XK engine parts, and would take some weeks to order them in. And you really never know what the aftermarket specialist suppliers are selling you, especially now that a number of them sell aftermarket/Chinese made items not subject to any competent design nor quality control under the original Jaguar Part Number.
I am not saying there are NO suitable aftermarket bolt/nut solutions, just how does the average person know exactly what they are getting - with original bolts/nuts they are on hand, and you know what they are.
Very few aftermarket suppliers, can guarantee whether critical bolts are essential high-tensile, mild-steel, or recycled coke cans, regardless of any so intended markings on the bolt head…
Maybe just ‘new split pins’ then, and forget the ‘modern’
Actually some years ago I did an engineering audit on a new car manufacturer in Malaysia, that was using split-pins and slotted nuts on many of their suspension joints. I had to show their engineering manager the correct way of fitting/securing the split-pins!
PS. Although a NEW car manufacturer, they were making MG TD replicas, that had passed all Australia’s mandatory safety requirements (with a number of specific low volume occupant protection
concessions - no crash testing) to be sold new in Australia, thus subject to engineering audit
That’s why I never reuse them. I’m not qualified to examine and say that they are anything other than used. I’m only throwing away 12 bolts.
Zero lost sleep.
I’ve got a new set coming from Barrett, who shows them as “OE (Original Equipment)”. They’ve got a knurled shank. We’ll see if they finger-press fit into the bore and sit tight at the cap. Given that they sent me a bronze alloy clutch fork that was marked “Steel” (no longer marked as being steel on their site, good for them), … we’ll see.
That sounds fascinating.
The MiL-spec bolts I got from SNG required a light tapping, with a plastic mallet. No biggie.
Tony, I would say “barely” adequate as when Jaguar introduced the 4.2 they reduced the RPM red line by 500 rpm. to 5000 because they experienced rod bolt failures.
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That blowup was not because of inherent issues with the bolt strength: it was because of the fit issue, and a tach that was reading (IIRC) 500 rpm, too low.
Properly fitted, I’d have NO issue with ARP bolts. They held up quite well at 10 grand, in my Datsun…
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We’ve got it good.
Anyone want to talk to a buddy restoring a 1911 Cadillac? He had to put a Bridgeport mill and a lathe in his garage because he got tired of going to the local machine shop to have parts altered to fit.
when i was fitting new con rod bolts for Diesel engines , i used a Hydraulic press , and tool with a hole in it, for bottom and steel 1" dia rod for pushing the bolt into the rod hole! it seems to me they had a slight chamfer at top!
musta worked never had a come back!
beating the bolt in with a hammer just is not my style, butcher work! could cause an unseen fracture!
ron
Got a reference for this?
i like ARP products , they are ahead of most Nut& Bolt stuff than anyone else in the world!
NOT counting F1 zillion money!
ron
1911 Cadillac?
I would think in 1911 Cadillac would have done a lot of that ‘fettling’ themselves.
Reminds me of a report I wrote from a very early visit to Jaguar Classic when they were just starting out. They were laser-scanning an early (and not pristine) E-type FHC and boasted they would produce panels of unsurpassed accuracy. I said it was a nice idea but if they produced perfect panels they wouldn’t fit many real-word cars.
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I got my beginnings of machine shop training, when I did a full mechanical restoration of a 1923 Kelly-Springfield fire truck.
Surprise! NAPA carries no parts for it…!
Perhaps the 75% to 90% of elastic range (called yield strength at range max) properly accounts for fatigue failure, endurance limit issues for most applications.
Example: Grade 8 steel with about 1,000 MPa tensile strength and 900 MPa yield strength shows in Table 2 in one study, Marcelo, A.L., et al, in Procedia Engineering 10 (2011) 1297-1302 titled Fatigue Properties of High Strength Bolts, to have around 850 MPa fatigue limit. An ASM International publication, link below, shows in Table 14.5 a range of about 600 to 740 MPa fatigue limit for grade 8 steel.
At 900 MPa yield strength that gives a range of 600/900 to 850/900 equal to a range of 66% to about 94% of yield strength, consistent with the engineering recommendation of 75% to 90% which is commonly used.
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